This invention relates generally to vehicles and specifically to a folding motorized chair with mechanical traction control that folds flat and is light enough for a person to lift into the trunk of a car.
Contemporary power chairs may be divided into two categories: those that steer by selectively operated traction wheels and those that steer by turning the front wheel or wheels.
The traction-steered vehicles are commonly referred to as power wheelchairs. They have front casters and are controlled by a single joystick that interacts with a very complicated electronic control system for switching and modulating the requisite high current, low voltage, battery power. Power wheelchairs employ two gear motors to independently and directly drive the left and right traction wheels. These motors in various combinations of power input; propel, steer and brake the vehicle. It should be noted that, due to the requisite high ratio gearing of the vehicle, it is impossible to overdrive the motors (to allow the vehicle to coast) when traveling downhill. This inability to coast reduces its range of travel, particularly in graded or hilly areas. The two gear motors require large and heavy batteries to provide an acceptable range of travel. The excessive weight of power wheelchairs makes it humanly impossible to lift them off the ground so a van equipped with a mechanical lift or a loading ramp is needed to transport them. A further drawback of power wheelchairs is high cost, not only of the vehicle but of the specially equipped van as well.
Power chairs that directly steer a wheel (or a pair of wheels) are commonly referred to as scooters. Most scooters employ a tricycle configuration with steering of the front wheel being accomplished by means of a handlebar. This configuration results in far too large a turning radius for indoor maneuvering. Even in a large indoor area the front upright steering column precludes indoor activities like sitting at a desk or table. Scooters employ a single gear motor that drives the rear wheels through a differential. The differential is subject to traction loss due to split coefficient. This may occur for example, when either drive wheel loses traction on a wet or slippery surface resulting in neither drive wheel being able to provide a driving force. The result is that the vehicle user, who is often incapable of walking or significant unassisted movement, is literally stranded.
Because of their front wheel steering and tricycle configuration, scooters are highly unstable at practically all speeds. A sudden turn of the handlebar will cause the tricycle to tip. The centrifugal force acting on such a high center of gravity vehicle tends to throw the vehicle (and occupant) up onto the front wheel and the outside drive wheel. If the occupant does not immediately steer out of the turn (which is sometimes impossible) a rollover will occur.
The gear motor, differential drive and frame structure needed to support a front handlebar steering system makes the cost and weight only slightly reduced as compared to the joy stick controlled power wheelchairs discussed above. The size and weight of these vehicles is impossible to fit in the trunk of a car. A van equipped with a mechanical lift or loading ramp is needed to transport scooters. A further draw back of the scooters is cost. The sheer size and weight contribute to the cost not only of the scooter but the specially equipped van as well.
There are some scooters of relatively lighter weight but they are still too heavy to be manually lifted and too big to fit in a car trunk. These down-sized scooters have very poor performance and are limited to mild hills and smooth terrain. Some of these scooters can be taken apart by removing the upright steering column, the seat, and finally the battery pack. The components can be loaded into a car trunk piece by piece but assembly in a parking lot is inconvenient and dangerous. The battery pack is the heaviest part that in most cases weighs more than the weight of the present invention in its entirety, battery included.